1. Field of the Invention
The present invention relates to pulse combustion devices using flapper-type air and gas inlet valves, and more particularly to an air inlet valve assembly in the pulse combustion device.
2. Description of the Prior Art
In U.S. Pat. No. 4,715,807 issued on Dec. 29, 1987 there has been proposed a pulse combustion device which includes a housing forming therein a combustion chamber, a cylindrical support member joined to the housing to form a mixing chamber in open communication with the combustion chamber, an annular perforated flange member coupled with an open end of the support member, a cylindrical member mounted in the center of the flange member to form a gas passage in open communication with the mixing chamber, an annular valve plate formed with a plurality of circumferentially equally spaced air ports and being secured to annular end surfaces of the flange member and the cylindrical member, a flapper-type gas inlet valve unit disposed within the cylindrical member, and a plurality of circumferentially equally spaced air inlet valve units mounted on the valve plate in surrounding relationship with the gas passage.
In such a pulse combustion device as described above, a cup-shaped distribution head is secured to an inner end of the cylindrical member to protect the gas inlet valve unit from radiant heat of the combustion products applied from the combustion chamber. However, the air inlet valve units are directly exposed to the radiant heat of the combustion products. As a result, durability of the air inlet valve units is deteriorated in a short period of time. Such a problem will arise particularly in a pulse combustion device in which the air inlet valve units are arranged adjacent the central portion of the mixing chamber to increase combustion capacity of the device.